Cutting tool

ABSTRACT

A cutting tool comprises a substrate and an AlTiN layer, the AlTiN layer including a first major surface and a second major surface, the AlTiN layer including a first region having a distance of 0 nm or more and 30 nm or less from the first major surface and having a maximum oxygen content ratio of 30 atomic % or more, a second region having a distance of more than 30 nm and 100 nm or less from the first major surface and having a maximum oxygen content ratio of 5 atomic % or more and less than 30 atomic %, and a third region having a distance exceeding 100 nm from the first major surface and having a maximum oxygen content ratio of less than 5 atomic %.

TECHNICAL FIELD

The present disclosure relates to a cutting tool.

BACKGROUND ART

Conventionally, cutting tools made of cemented carbide or cubic boronnitride (cBN) sintered material have been used to cut steel, castings,and the like. When such a cutting tool is used to cut a workpiece thecutting tool has its cutting edge exposed to a severe environment suchas high temperature and high stress, which invites wearing and chippingof the cutting edge.

Accordingly, suppressing wearing and chipping of the cutting edge isimportant in improving the cutting performance of the cutting tool andhence extending the life of the cutting tool.

For the purpose of improving a cutting tool's cutting performance (e.g.,breaking resistance and wear resistance) a development of a coating forcoating a surface of a substrate of cemented carbide, cBN sinteredmaterial and the like is underway. Inter alia, a coating composed of acompound of aluminum (Al), titanium (Ti), and nitrogen (N) (hereinafteralso referred to as “AlTiN”) can have high hardness and also enhanceoxidation resistance (for example, see Japanese Patent Laid-Open No.10-330914 (PTL 1)).

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 10-330914

SUMMARY OF INVENTION

The presently disclosed cutting tool is

a cutting tool comprising a substrate and an AlTiN layer disposed on thesubstrate,

the AlTiN layer including cubic Al_(x)Ti_((1-x))N crystal grains,

an atomic ratio x of Al in the Al_(x)Ti_((1-x))N being 0.7 or more and0.95 or less,

the AlTiN layer including a first major surface on a side of a surfaceof the cutting tool and a second major surface on a side of thesubstrate,

the AlTiN layer including a first region having a distance of 0 nm ormore and 30 nm or less from the first major surface, a second regionhaving a distance of more than 30 nm and 100 nm or less from the firstmajor surface, and a third region having a distance exceeding 100 nmfrom the first major surface,

the first region having a maximum oxygen content ratio of 30 atomic % ormore,

the second region having a maximum oxygen content ratio of 5 atomic % ormore and less than 30 atomic %,

the third region having a maximum oxygen content ratio of less than 5atomic %.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a cutting tool according to a firstembodiment.

FIG. 2 illustrates another example of the cutting tool according to thefirst embodiment.

FIG. 3 illustrates still another example of the cutting tool accordingto the first embodiment.

FIG. 4 illustrates an AlTiN layer of the cutting tool according to thefirst embodiment.

FIG. 5 is a schematic cross section of a CVD apparatus used formanufacturing a cutting tool according to a second embodiment.

FIG. 6 is a schematic cross section of a gas introduction pipe of theCVD apparatus of FIG. 5.

DETAILED DESCRIPTION Problem to be Solved by the Present Disclosure

In recent years, a cutting tool having a long tool life has also beendemanded for a more efficient cutting process. In cutting chromiummolybdenum steel, in particular, there is a demand for a cutting toolexcellent in welding resistance and wear resistance.

Advantageous Effect of the Present Disclosure

The presently disclosed cutting tool can also have a long tool life evenin cutting chromium molybdenum steel in particular.

DESCRIPTION OF EMBODIMENTS OF THE PRESENT DISCLOSURE

Initially, embodiments of the present disclosure will be listed anddescribed.

(1) The presently disclosed cutting tool is

a cutting tool comprising a substrate and an AlTiN layer disposed on thesubstrate,

the AlTiN layer including cubic Al_(x)Ti_((1-x))N crystal grains,

an atomic ratio x of Al in the Al_(x)Ti_((1-x))N being 0.7 or more and0.95 or less,

the AlTiN layer including a first major surface on a side of a surfaceof the cutting tool and a second major surface on a side of thesubstrate,

the AlTiN layer including a first region having a distance of 0 nm ormore and 30 nm or less from the first major surface, a second regionhaving a distance of more than 30 nm and 100 nm or less from the firstmajor surface, and a third region having a distance exceeding 100 nmfrom the first major surface,

the first region having a maximum oxygen content ratio of 30 atomic % ormore,

the second region having a maximum oxygen content ratio of 5 atomic % ormore and less than 30 atomic %,

the third region having a maximum oxygen content ratio of less than 5atomic %.

The presently disclosed cutting tool can also have a long tool life evenin cutting chromium molybdenum steel in particular.

(2) The first region preferably has a maximum oxygen content ratio of 30atomic % or more and 50 atomic % or less. The presently disclosedcutting tool can thus have a longer tool life.

(3) The AlTiN layer preferably has a thickness of 0.1 μm or more and 20μm or less. The presently disclosed cutting tool can thus have a longertool life.

(4) Preferably, the cutting tool further comprises an underlying layerdisposed between the substrate and the AlTiN layer, wherein

the underlying layer is composed of a first compound consisting of atleast one element selected from the group consisting of a group 4element, a group 5 element and a group 6 element of the periodic tableand Al and at least one element selected from the group consisting ofcarbon, nitrogen, oxygen and boron.

This can enhance the AlTiN layer in peeling resistance.

(5) Preferably, the cutting tool further comprises a surface layerdisposed on the AlTiN layer, wherein

the surface layer is composed of a second compound consisting of atleast one element selected from the group consisting of a group 4element, a group 5 element and a group 6 element of the periodic tableand Al and at least one element selected from the group consisting ofcarbon, nitrogen, oxygen and boron.

The presently disclosed cutting tool can thus have a further longer toollife.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT DISCLOSURE

A specific example of the present disclosed cutting tool will now bedescribed below with reference to the drawings. In the drawings of thepresent disclosure, like reference numerals denote like or equivalentcomponents. Furthermore, in the drawings, length, width, thickness,depth and other similar dimensional relationships are changed asappropriate for clarification and simplification of the drawings, andmay not represent actual dimensional relationships.

In the present specification, an expression in the form of “A to B”means a range's upper and lower limits (that is, A or more and B orless), and when A is not accompanied by any unit and B is aloneaccompanied by a unit, A has the same unit as B.

In the present specification, when a compound or the like is representedby a chemical formula without specifying any specific atomic ratio, itshall include any conventionally known atomic ratio and should notnecessarily be limited to what falls within a stoichiometric range. Forexample, “AlTiN” has a ratio in atomicity including any conventionallyknown atomic ratio.

First Embodiment: Cutting Tool

The presently disclosed cutting tool is

a cutting tool comprising a substrate and an AlTiN layer disposed on thesubstrate,

the AlTiN layer including cubic Al_(x)Ti_((1-x))N crystal grains,

an atomic ratio x of Al in the Al_(x)Ti_((1-x))N being 0.7 or more and0.95 or less,

the AlTiN layer including a first major surface on a side of a surfaceof the cutting tool and a second major surface on a side of thesubstrate,

the AlTiN layer including a first region having a distance of 0 nm ormore and 30 nm or less from the first major surface, a second regionhaving a distance of more than 30 nm and 100 nm or less from the firstmajor surface, and a third region having a distance exceeding 100 nmfrom the first major surface,

the first region having a maximum oxygen content ratio of 30 atomic % ormore,

the second region having a maximum oxygen content ratio of 5 atomic % ormore and less than 30 atomic %,

the third region having a maximum oxygen content ratio of less than 5atomic %.

The presently disclosed cutting tool can also have a long tool life evenin cutting chromium molybdenum steel in particular. Although why it cando so is not known, it is inferred as indicated by items (i) and (ii)below:

(i) In the presently disclosed cutting tool, the AlTiN layer has amaximum oxygen content ratio of 30 atomic % or more in the first regionlocated on a side of an outermost surface thereof. The first region thushas excellent welding resistance. The cutting tool can thus have a longtool life.

(ii) In the presently disclosed cutting tool, the AlTiN layer has amaximum oxygen content ratio of S atomic % or more and less than 30atomic % in the second region and a maximum oxygen content ratio of lessthan 5 atomic % in the third region. The second and the third regionsthus have high hardness and excellent wear resistance. The cutting toolcan thus have a long tool life.

<Configuration of Cutting Tool>

As shown in FIG. 1, a cutting tool 1 of the present embodiment comprisesa substrate 10, and an AlTiN layer 11 disposed on substrate 10(hereinafter also simply referred to as a “cutting tool”).

As shown in FIG. 2, a cutting tool 21 may further comprise an underlyinglayer 12 disposed between substrate 10 and AlTiN layer 11.

As shown in FIG. 3, a cutting tool 31 may further comprise a surfacelayer 13 disposed on AlTiN layer 11. Other layers such as underlyinglayer 12 and surface layer 13 will be described hereinafter.

In the present specification, the above-described layers disposed onsubstrate 10 may be collectively referred to as a “coating.” That is, asshown in FIGS. 1 to 3, cutting tools 1, 21 and 31 comprise coatings 14,24 and 34 disposed on substrate 10, and the coatings include AlTiN layer11. Further, as shown in rigs. 2 and 3, coatings 24 and 34 may furtherinclude underlying layer 12 and/or surface layer 13.

<Applications of Cutting Tool>

The cutting tool can for example be a drill, an end mill (e.g., a ballend mill), an indexable cutting insert for a drill, an indexable cuttinginsert for an end mill, an indexable cutting insert for milling, anindexable cutting insert for turning, a metal saw, a gear cutting tool,a reamer, a tap, or the like.

<Substrate>

The substrate of the present embodiment can be any substrateconventionally known as a substrate of this type. For example, itpreferably includes at least one selected from the group consisting of acemented carbide (for example, a tungsten carbide (WC)-base cementedcarbide, a cemented carbide containing WC and Co, a cemented carbidecontaining WC and a carbonitride of Cr, Ti, Ta, Nb or the like, and thelike), a cermet (mainly composed of TiC, TiN, TiCN, or the like), ahigh-speed steel, ceramics (titanium carbide, silicon carbide, siliconnitride, aluminum nitride, aluminum oxide, and the like), a cubic boronnitride (cBN) sintered material, and a diamond sintered material.

Of these various types of substrates, it is particularly preferable toselect a cemented carbide (a WC-base cemented carbide, in particular) ora cermet (a TiCN-base cermet, in particular). This is because thesesubstrates are particularly excellent in balance between hardness andstrength at high temperature, in particular, and present excellentcharacteristics as a substrate for a cutting tool for theabove-described applications.

When using a cemented carbide as a substrate, the effect of the presentembodiment is exhibited even if the cemented carbide has a structureincluding free carbon or an extraordinary phase referred to as η phase.Note that the substrate used in the present embodiment may have itssurface modified. For example, for the cemented carbide, the surface maybe provided with a R-free layer, and for the cermet, the surface may beprovided with a surface hardened layer, and even if the surface ismodified in this way, the effect of the present embodiment is exhibited

<Coating>

A coating according to the present embodiment includes an AlTiN layerdisposed on the substrate. The “coating” coats at least a part of thesubstrate (for example, a rake face, a flank, and the like) to exhibit afunction to improve the cutting tool's various characteristics such asbreaking resistance, wear resistance, peeling resistance and the like.The coating is preferably applied not only to a part of the substratebut also to the entire surface of the substrate. However, even if thesubstrate is partially uncoated with the coating or the coating ispartially different in configuration, such does not depart from thescope of the present embodiment.

The coating's thickness is preferably 2.5 μm or more and 30 μm or less,more preferably 3 μm or more and 25 μm or less. Note that the thicknessof the coating means a total thickness of any layers constituting thecoating. A “layer constituting the coating” for example includes anAlTiN layer, an underlying layer, a surface layer and the like, as willbe described hereinafter.

Each layer configuring the coating is measured in thickness by observingwith a scanning transmission electron microscope (STEM) a sample in across section parallel to the direction of a normal to a surface of thesubstrate, for example. The scanning transmission electron microscope isJEM-2100F (trade name) manufactured by JEOL Ltd., for example.

As used herein. “thickness” means an average thickness. Specifically, asample in cross section is observed with a magnification of 5,000 to10,000 times in an area of 100 to 500 μm², and in one field of view, 10locations are subject to measurement in thickness in width and theiraverage value is determined as “thickness.”

<AlTiN Layer>

The AlTiN layer of the present embodiment includes cubic Al_(x)Ti_(1-x)Ncrystal grains (hereinafter also simply referred to as “crystalgrains”). That is, the AlTiN layer is a layer including polycrystallineAl_(x)Ti_(1-x)N. In the present embodiment, “crystal grains ofAl_(x)Ti_(1-x)N” mean crystal grains each of a composite crystal formedof a layer made of AlN (hereinafter also referred to as an “AlN layer”)and a layer made of TiN (hereinafter also referred to as a “TiN layer”)alternately stacked. In the present embodiment, the AlN layer alsoincludes a layer having a portion with Al substituted with Ti. Further,the TiN layer also includes a layer having a portion with Ti substitutedwith Al.

For cubic Al_(x)Ti_(1-x)N crystal grains, the AlN layer and the TiNlayer both have an FCC structure (Face-Centered Cubic structure).

An atomic ratio x of Al in the Al_(x)Ti_(1-x)N is 0.7 or more and 0.95or less, preferably 0.8 or more and 0.9 or less.

The x is determined by analyzing crystal grains in the AlTiN layerappearing in a sample in a cross section parallel to the direction of anormal to a surface of the substrate with an energy dispersive X-ray(EDX) spectrometer accompanying a scanning electron microscope (SEM) ora TEM. The atomic ratio x of Al thus determined is a value determined asan average of all of the crystal grains of the Al_(x)Ti_(1-x)N.Specifically, any 10 points in the AlTiN layer in a sample in theabove-described cross section is each measured to obtain a value x, andan average value of such values obtained at the 10 points is defined asx in the Al_(x)Ti_(1-x)N. Herein, “any 10 points” are selected fromdifferent crystal grains of the AlTiN layer. The EDX device is JED-2300(trade name) manufactured by JEOL Ltd., for example. Not only the atomicratio of Al but those of Ti and N can also be calculated in the abovemethod.

In the present embodiment, being “disposed on the substrate” is notlimited to being disposed directly on the substrate and also includesbeing disposed on the substrate via another layer. That is, the AlTiNlayer may be disposed directly on the substrate or may be disposed onthe substrate via another layer such as an underlying layer describedhereinafter insofar as such does not impair an effect of thesurface-coated cutting tool according to the present embodiment.

On the AlTiN layer, another layer such as a surface layer may bedisposed. The AlTiN layer may be an outermost surface layer of thecoating.

As shown in FIG. 4, AlTiN layer 11 includes a first major surface 11 aon a side of a surface of cutting tool 1 and a second major surface 11 bon a side of substrate 10. AlTiN layer 11 includes a first region 11Ahaving a distance of 0 nm or more and 30 nm or less from first majorsurface 11 a, a second region 11B having a distance of more than 30 nmand 100 nm or less from first major surface 11 a, and a third region 11Chaving a distance exceeding 100 nm from first major surface 11 a. Thirdregion 11C can have a distance of more than 100 nm and 200 nm or lessfrom the first main surface.

In the AlTiN layer of the present embodiment, the first region has amaximum oxygen content ratio of 30 atomic % or more. The first regionthus has excellent welding resistance. The cutting tool can thus have along tool life.

The first region has the maximum oxygen content ratio with a lower limitof 30 atomic % or more, and the lower limit can be 31 atomic % or more.The first region can have the maximum oxygen content ratio with an upperlimit of 50 atomic % or less, 45 atomic % or less. The first region canhave a maximum oxygen content ratio of 30 atomic % or more and 50 atomic% or less, 31 atomic % or more and 45 atomic % or less.

In the present specification, the AlTiN layer's oxygen content ratio (asconverted to SiO₂) is measured while etching a surface of a diamondlayer using an Auger electron spectrometer (AES) (device: PHI 650®produced by Perkin-Elmer) in accordance with JIS K 0146:2002 (ISO14606:2000) while etching the AlTiN layer in the direction of a normalto the first major surface.

The etching is performed in a direction from the first major surfacetoward the second major surface (hereinafter also referred to as a“depthwise direction”) in the direction of a normal to the first majorsurface. The oxygen content ratio is measured at points at intervals of2 nm in the depthwise direction of the AlTiN layer. Thus, the oxygencontent ratio can be measured at intervals of 2 nm in the depthwisedirection of the AlTiN layer.

The Auger electron spectroscopic measurement is conducted under thefollowing conditions:

Electron Energy: 10 kv

Electron beam current: 3 mA

Angle of incidence: 90°

(Detector: 55°)

Beam diameter: 1 nm

Sputter ion: Ar

Mode: Depth Analysis (Depth Profile)

Note that, as measured by the applicant, it has been confirmed that, asmeasured in the same sample, while the AlTiN layer's oxygen contentratio was measured a plurality of times while where it was measured waschanged, measurement results were obtained without substantial variationand there was no arbitrariness even when where it was measured was setas desired Where it is measured can for example be the cutting tool'srake face, cutting edge, or the like.

The second region has a maximum oxygen content ratio of 5 atomic % ormore and less than 30 atomic %. The second region thus has high hardnessand excellent wear resistance. The cutting tool can thus have a longtool life.

The second region has the maximum oxygen content ratio with a lowerlimit of 5 atomic % or more, and the lower limit can be 7 atomic % ormore. The second region can have the maximum oxygen content ratio withan upper limit of less than 30 atomic % and the upper limit can be 28atomic % or less. The second region can have a maximum oxygen contentratio of 5 atomic % or more and less than 30 atomic %, 7 atomic % ormore and 28 atomic % or less.

The third region has a maximum oxygen content ratio of less than 5atomic %. The third region thus has high hardness and excellent wearresistance. The cutting tool can thus have a long tool life.

The third region has the maximum oxygen content ratio with an upperlimit of less than 5 atomic %, and the upper limit can be 4 atomic % orless. The third region can have the maximum oxygen content ratio with alower limit of 0 atomic % or more, 1 atomic % or more. The third regioncan have a maximum oxygen content ratio of 0 atomic % or more and lessthan 5 atomic %, 1 atomic % or more and 4 atomic % or less.

The AlTiN layer preferably has a thickness of 0.1 μm or more and 20 μmor less. The cutting tool can thus have a longer tool life.

The AlTiN layer can have a lower limit in thickness of 0.1 μm or more, 1μm or more. The AlTiN layer can have an upper limit in thickness of 20μm or less, 10 μm or less. The AlTiN layer can be 0.1 μm or more and 20μm or less, 1 μm or more and 10 μm or less in thickness.

The AlTiN layer's thickness can be determined by observing a sample incross section of the cutting tool with a scanning transmission electronmicroscope (STEM) or the like, as has been described above.

<Underlying Layer>

As shown in FIGS. 2 and 3, cutting tools 21 and 31 comprise coatings 24and 34, respectively, which can further include underlying layer 12disposed between substrate 10 and AlTiN layer 11. Underlying layer 12 ispreferably composed of a first compound consisting of at least oneelement selected from the group consisting of a group 4 element, a group5 element and a group 6 element of the periodic table and Al and atleast one element selected from the group consisting of carbon,nitrogen, oxygen and boron. Examples of the group 4 element of theperiodic table include titanium (Ti), zirconium (Zr), hafnium (Hf), andthe like. Examples of the group 5 element of the periodic table includevanadium (V), niobium (Nb), tantalum (Ta), and the like. Examples of thegroup 6 element of the periodic table include chromium (Cr), molybdenum(Mo), tungsten (W), and the like.

The first compound is different in composition from the AlTiN layer.That is, when the first compound is AlTiN, the first compound has acomposition different from Al_(x)Ti_((1-x))N constituting the AlTiNlayer.

The underlying layer is preferably composed of a first compoundrepresented by TiCN. The underlying layer composed of TiCN exhibitsstrong adhesion to the AlTiN layer. As a result, the coating is enhancedin peeling resistance.

The underlying layer can have a lower limit in thickness of 0.1 μm ormore, 1 μm or more, 1.5 μm or more. The underlying layer can have anupper limit in thickness of 20 μm or less, 15 μm or less, 10 μm or less.The underlying layer can be 0.1 m or more and 20 μm or less, 1 μm ormore and 15 μm or less, 1.5 μm or more and 10 μm or less in thickness.

The underlying layer's thickness can be determined by observing a samplein cross section of the cutting tool with a scanning transmissionelectron microscope (STEM) or the like, as has been described above.

<Surface Layer>

As shown in FIG. 3, cutting tool 31 comprises coating 34 which canfurther include surface layer 13 disposed on AlTiN layer 11. Surfacelayer 13 is composed of a second compound consisting of at least oneelement selected from the group consisting of a group 4 element, a group5 element and a group 6 element of the periodic table and Al and atleast one element selected from the group consisting of carbon,nitrogen, oxygen and boron.

The second compound is different in composition from the AlTiN layer.That is, when the second compound is AlTiN, the second compound has acomposition different from Al_(x)Ti_((1-x))N constituting the AlTiNlayer.

Examples of the second compound include Al₂O₃ and TiN.

The surface layer can have a lower limit in thickness of 0.1 μm or more,0.2 μm or more. The surface layer can have an upper limit in thicknessof 3 μm or less, 2 μm or less, 1 μm or less. The surface layer can be0.1 μm or more and 3 μm or less, 0.2 μm or more and 2 μm or less, 0.2 μmor more and 1 μm or less in thickness.

The surface layer's thickness can be determined by observing a sample incross section of the cutting tool with a scanning transmission electronmicroscope (STEM) or the like, as has been described above.

<Another Layer>

The coating of the cutting tool may further include another layerinsofar as it does not impair an effect of the cutting tool according tothe present embodiment. The other layer may have a composition differentfrom or identical to that of the AlTiN layer, the underlying layer, orthe surface layer. Examples of a compound included in the other layerinclude TiN, TiCN, TiBN, and Al₂O₃. The other layer is not limited,either, in in what order it is stacked. For example, an example of theother layer is an intermediate layer disposed between the underlyinglayer and the AlTiN layer. While the other layer is not particularlylimited in thickness as long as it does not impair an effect of thepresent embodiment, it is for example 0.1 μm or more and 20 μm or less.

Second Embodiment: A Method for Manufacturing a Cutting Tool

While a method for manufacturing a cutting tool according to the firstembodiment is not particularly limited, it for example comprises a firststep of preparing the substrate (hereinafter also simply referred to asa “first step”), and a second step of depositing a coating including theAlTiN layer on the substrate through chemical vapor deposition (CVD)(hereinafter also simply referred to as a “second step”). The method formanufacturing the cutting tool according to the present embodiment canfurther comprise a third step of blasting the coating (hereinafter alsoreferred to as a “third step”). An example of the method formanufacturing the cutting tool according to the first embodiment will bedescribed below. Note that the following manufacturing method is anexample, and the method of manufacturing the cutting tool according tothe first embodiment is not limited to the following method and thecutting tool may be manufactured in a different method.

<First Step: Step of Preparing a Substrate>

In the first step, a substrate is prepared. For example, a cementedcarbide substrate, a cermet substrate or the like is prepared as thesubstrate. The cemented carbide substrate may be a commerciallyavailable product or may be manufactured in a typical powder metallurgymethod. When the substrate is manufactured in a typical powdermetallurgy method, for example, WC powder and Co powder or the like aremixed using a ball mill or the like to obtain a powdery mixture. Afterthe powdery mixture is dried, it is shaped into a prescribed shape toobtain a shaped body. The shaped body is sintered to obtain a WC—Cobased cemented carbide (a sintered material).

Subsequently, the sintered material can be honed or subjected to aprescribed cutting edge process to prepare a substrate made of the WC—Cobased cemented carbide. In the first step, any other substrate may beprepared insofar as it is a substrate conventionally known as asubstrate of this type.

<Second Step: Step of Forming an AlTiN Layer>

In the second step, a first gas, a second gas and a third gas are jettedonto the substrate in an atmosphere of 650° C. or higher and 800° C. orlower and 2 kPa or higher and 30 kPa or lower, the first gas including agas of a halide of aluminum, a gas of a halide of titanium, carbonmonoxide, carbon dioxide, and ethanol, the second gas including a gas ofa halide of aluminum, a gas of a halide of titanium and a gas ofammonia, the third gas including a gas of ammonia. The second step canbe performed using, for example, a CVD apparatus described below.

(CVD Apparatus)

FIG. 5 is a schematic cross section of one example of a CVD apparatusused for manufacturing the cutting tool according to the presentembodiment. As shown in FIG. 5, a CVD apparatus 50 includes a pluralityof substrate setting jigs 52 for setting substrate 10, and a reactionchamber 53 made of heat-resistant alloy steel and incorporatingsubstrate setting jigs 52 therein. A temperature controller 54 isprovided around reaction chamber 53 for controlling the temperatureinside reaction chamber 53. In the present embodiment, substrate 10 isset on a protrusion which substrate setting jig 52 is provided with.Such a setting allows deposition to be done on a rake face, a flank, anda cutting edge portion uniformly.

A gas introduction pipe 58 having a first gas introduction pipe 55, asecond gas introduction pipe 56 and a third gas introduction pipe 57adjacently bonded together extends in the vertical direction through aspace inside reaction chamber 53 rotatably about the vertical direction.Gas introduction pipe 58 is configured such that the first gasintroduced into first gas introduction pipe 55, the second gasintroduced into second gas introduction pipe 56, and the third gasintroduced into third gas introduction pipe 57 are not mixed togetherinside gas introduction pipe 58 (see FIG. 6). Further, first gasintroduction pipe 55, second gas introduction pipe 56, and third gasintroduction pipe 57 are each provided with a plurality of throughholesfor jetting the gases respectively flowing through first, second andthird gas introduction pipes 55, 56 and 57 onto substrate 10 set onsubstrate setting jig 52. In the present embodiment, it is preferablethat the gas jetting throughhole and substrate 10 be spaced by asufficient distance. This allows the first gas, the second gas, and thethird gas to flow uniformly and can thus prevent turbulence.

Further, reaction chamber 53 is provided with a gas exhaust pipe 59 forexternally exhausting the gas inside reaction chamber 53, and the gas inreaction chamber 53 passes through gas exhaust pipe 59 and is exhaustedout of reaction chamber 53 via a gas exhaust port 60.

More specifically, the first gas, the second gas and the third gas areintroduced into first gas introduction pipe 55, second gas introductionpipe 56 and third gas introduction pipe 57, respectively. In doing so,the first, second and third gases in their respective gas introductionpipes may have any temperature that does not liquefy the gases.Subsequently, the first gas, the second gas and the third gas are jettedin this order repeatedly into reaction chamber 53 with an atmosphere settherein to have a temperature of 650° C. or higher and 800° C. or lowerand a pressure of 2 kPa or higher and 30 kPa or lower. As gasintroduction pipe 58 has the plurality of throughholes, the first,second, and third gases introduced are jetted into reaction chamber 53through different throughholes, respectively. While the gases are thusjetted, gas introduction pipe 58 is rotating at a rotation speed forexample of 2 to 4 rpm about the above-described axis, as indicated inFIG. 5 by a rotating arrow. As a result, the first gas, the second gas,and the third gas can be jetted in this order repeatedly onto substrate10.

(First Gas)

The first gas includes a gas of a halide of aluminum, a gas of a halideof titanium, carbon monoxide, carbon dioxide, and ethanol.

Examples of the gas of a halide of aluminum include a gas of aluminumchloride (a gas of AlCl₃ and a gas of Al₂Cl₆). Preferably, a gas ofAlCl₃ is used. The gas of a halide of aluminum preferably has aconcentration (% by volume) of 0.1% by volume or more and 20% by volumeor less with reference to the total volume of the first gas.

Examples of the gas of a halide of titanium include a gas of titanium(IV) chloride (a gas of TiCl₄), a gas of titanium (III) chloride (a gasof TiCl₃), and the like. Preferably a gas of titanium (IV) chloride isused. The gas of a halide of titanium preferably has a concentration (in% by volume) of 0.1% by volume or more and 20% by volume or less withreference to the total volume of the first gas.

In the first gas, the gas of a halide of aluminum has a molar ratio morepreferably of 0.1 or more and 0.9 or less with reference to the totalmoles of the gas of a halide of aluminum and the gas of a halide oftitanium.

Carbon monoxide, carbon dioxide, and ethanol preferably have aconcentration (in % by volume) of 0.1% by volume or more and 20% byvolume or less with reference to the total volume of the first gas.

The first gas may include a gas of hydrogen and may include an inert gassuch as a gas of argon. The inert gas preferably has a concentration (in% by volume) of 10% by volume or more and 60% by volume or less withreference to the total volume of the first gas. The gas of hydrogentypically occupies the balance of the first gas.

The first gas is jetted onto the substrate at a flow rate preferably of5 to 60 L/min.

(Second Gas)

The second gas includes a gas of a halide of aluminum, a gas of a halideof titanium, and a gas of ammonia. The gas of a halide of aluminum andthe gas of a halide of titanium can be the gases exemplified in theabove (First Gas) section. The gas of a halide of aluminum and the gasof a halide of titanium that are used for the first gas may be identicalto or different from the gas of a halide of aluminum and the gas of ahalide of titanium that are used for the second gas, respectively.

The gas of a halide of aluminum preferably has a concentration (% byvolume) of 2% by volume or more and 50% by volume or less with referenceto the total volume of the second gas.

The gas of a halide of titanium preferably has a concentration (in % byvolume) of 0.1% by volume or more and 20% by volume or less withreference to the total volume of the second gas.

In the second gas, the gas of a halide of aluminum has a molar ratiopreferably of 0.1 or more and 0.9 or less with reference to the totalmoles of the gas of a halide of aluminum and the gas of a halide oftitanium.

The gas of ammonia preferably has a concentration (in % by volume) of0.1% by volume or more and 20% by volume or less with reference to thetotal volume of the second gas.

The second gas may include a gas of hydrogen and may include an inertgas such as a gas of argon. The inert gas preferably has a concentration(in % by volume) of 0.1% by volume or more and 20% by volume or lesswith reference to the total volume of the second gas. The gas ofhydrogen typically occupies the balance of the second gas.

The second gas is jetted onto the substrate at a flow rate preferably of5 to 60 L/min.

(Third Gas)

The third gas includes a gas of ammonia. The third gas may include a gasof hydrogen and may include an inert gas such as a gas of argon.

The gas of ammonia preferably has a concentration (in % by volume) of0.1% by volume or more and 40% by volume or less with reference to thetotal volume of the third gas. The gas of hydrogen typically occupiesthe balance of the third gas.

The third gas is jetted onto the substrate at a flow rate preferably of5 to 20 L/min.

<Third Step: Blasting Step>

In the present step, the coating is blasted. The blasting is performedfor example under the following conditions. The blasting allowscompressive residual stress to be imparted to the coating.

(Blasting Conditions)

Medium: 500 g of zirconia particles

Projection angle: 90°

Projection distance: 50 mm

Projection time: 3 seconds

<Another Step>

In the manufacturing method according to the present embodiment, inaddition to the steps described above, an additional step may beperformed, as appropriate, within a range that does not impair an effectof the present embodiment. Examples of the additional step include thestep of forming an underlying layer between the substrate and the AlTiNlayer, and the step of forming a surface layer on the AlTiN layer. Theunderlying layer and the surface layer may be formed in any method, andthe layers are formed for example through CVD. When the step of formingthe surface layer on the AlTiN layer is performed, the third step isperformed after the surface layer is formed.

In the method for manufacturing a surface-coated cutting tool accordingto the present embodiment, the AlTiN layer is formed through CVD. Whenthis is compared with forming the coating through PVD, the formerenhances the coating's adhesion to the substrate (or coating adhesion).

Examples

The present embodiment will be described more specifically withreference to examples. Note, however, that the present embodiment is notlimited to these examples.

<<Manufacturing a Cutting Tool>>

<Preparing the Substrate>

Initially, as a substrate, a substrate composed of cemented carbideindicated in Table 1 below (hereinafter also simply referred to as a“substrate”) was prepared (i.e., a first step). Powdery raw materials ofa blending composition (% by mass) shown in Table 1 were uniformly mixedto provide a powdery mixture. In Table 1, “balance” indicates that WCoccupies the balance of the blending composition (% by mass)

TABLE 1 substrate's blending composition (mass %) Co TiC TiCN Cr₃C₂ TaCWC 5.0 1.0 1.0 0.3 0.5 balance

Subsequently, the powdery mixture was pressure-formed into a prescribedshape and thereafter sintered for 1 to 2 hours at 1300 to 1500° C. toobtain a substrate (substrate shape: CNMG120408 N-GU).

<Depositing the Coating>

Subsequently, the CVD apparatus shown in FIG. 5 was employed to depositon the substrate a coating including an underlying layer, an AlTiNlayer, and a surface layer.

(Depositing the Underlying Layer)

Under conditions indicated in Table 2 for deposition, a reactant gashaving a composition indicated in Table 2 was jetted onto a surface ofthe substrate to deposit an underlying layer of TiCN.

TABLE 2 conditions for depositing underlying layer composition ofreactant gas TiCl₄ = 2.0 vol %, CH₃CN = 0.7 vol %, H₂ = balancetemperature 860° C. pressure 9 kPa gas flow rate 50.5 L/min(Depositing the AlTiN Layer)

Subsequently, for Samples 1 to 8, an AlTiN layer was deposited on theunderlying layer. Depositing the AlTiN layer was divided into a firsthalf and a second half by changing the first gas in type (i.e., thesecond step).

In the first half, under the conditions for deposition as indicated inTable 3 at the “conditions for depositing the AlTiN layer” column, thefirst gas specified in Table 8 at the “conditions for depositing theAlTiN layer,” “1st half” and “1st gas (table 4)” column (see table 4 forthe composition of the gas), the second gas having the compositionindicated in Table 5, and the third gas having the composition indicatedin Table 6 were jetted in this order repeatedly onto a surface of theunderlying layer to deposit an AlTiN layer. The first half's depositiontime is as indicated in Table 8 at the “conditions for depositing theAlTiN layer,” “1st half” and “time (min.)” column.

Subsequently, in the second half, under the conditions for deposition asindicated in Table 3 at the “conditions for depositing the AlTiN layer”column, the first gas specified in Table 8 at the “conditions fordepositing the AlTiN layer,” “2nd half” and “1st gas (table 4)” column(see table 4 for the composition of the gas), the second gas having thecomposition indicated in Table 5, and the third gas having thecomposition indicated in Table 6 were jetted in this order repeatedlyonto a surface of the underlying layer to deposit an AlTiN layer. Thesecond half's deposition time is as indicated in Table 8 at the“conditions for depositing the AlTiN layer,” “2nd half” and “time(min.)” column.

The substrate was set on a protrusion which the substrate setting jigwas provided with. Furthermore, the gas jetting throughhole and thesubstrate were spaced by a sufficient distance (for example of 5 cm).

TABLE 3 conditions for depositing AlTiN layer temperature 780° C.pressure 3 kPa rotational speed 2 rpm

TABLE 4 composition of 1st gas ID no. a b c d e f g AlCl₃ (vol %) 0.830.83 0.83 0.83 0.83 1.00 0.83 TiCl₄ (vol %) 0.17 0.17 0.17 0.17 0.170.00 0.17 AlCl₃/(AlCl₃ + TiCl₄) 0.83 0.83 0.83 0.83 0.83 1.00 0.83(molar ratio) Ar (vol %) 40 40 40 40 40 40 50 CO (vol %) 7 7.5 8 8.5 910 0 CO₂ (vol %) 7 7.5 8 8.5 9 10 0 C₂H₅OH (vol %) 6 5 4 3 2 0 0 H₂ (vol%) bal- bal- bal- bal- bal- bal- bal- ance ance ance ance ance ance ancegas flow rate (L/min) 20 20 20 20 20 20 20

TABLE 5 composition of 2nd gas AlCl₃ (vol %) 4.2 TiCl₄ (vol %) 0.7AlCl₃/(AlCl₃ + TiCl₄) 0.86 (molar ratio) NH₃ (vol %) 11 Ar (vol %) 16 H₂(vol %) balance gas flow rate (L/min) 40

TABLE 6 composition of 3rd gas NH₃ (vol %)  2 H₂ (vol %) balance gasflow rate (L/min) 10

For example, for Sample 1 shown in Table 8, in the first half, with atemperature of 780° C., a pressure of 3 kPa, and the gas introductionpipe having a rotational speed of 2 rpm set as conditions for deposition(see Table 3), the first gas indicated in Table 4 by an identificationnumber g (AlCl₃: 0.83% by volume, TiCl₄: 0.17% by volume, Ar: 60% byvolume, H₂: balance, and gas flow rate: 20 L/min.), the second gasindicated in Table 5 (AlCl₃: 4.2% by volume, TiCl₄: 0.7% by volume, NH₃:11% by volume, Ar: 16% by volume, H₂: balance, and gas flow rate: 40L/min.), and the third gas indicated in Table 6 (NH₃: 2% by volume, H₂:balance, and gas flow rate: 10 L/min.) were jetted in this orderrepeatedly onto a surface of the substrate to deposit an AlTiN layer.The first half's deposition time was 590 minutes.

Subsequently, in the second half, with a temperature of 780° C., apressure of 3 kPa, and the gas introduction pipe having a rotationalspeed of 2 rpm set as conditions for deposition (see Table 3), the firstgas indicated in Table 4 by an identification number a (AlCl₃: 0.83% byvolume, TiCl₄: 0.17% by volume, Ar: 40% by volume, CO: 7% by volume,CO₂: 7% by volume, C₂H₅OH: 6% by volume, H₂: balance, and gas flow rate:20 L/min.), the second gas indicated in Table 5 (AlCl₃: 4.2% by volume,TiCl₄: 0.7% by volume, NH₃: 11% by volume, Ar: 16% by volume, H₂:balance, and gas flow rate: 40 L/min.), and the third gas indicated inTable 6 (NH₃: 2% by volume, H₂: balance, and gas flow rate: 10 L/min.)were jetted in this order repeatedly onto a surface of the substrate todeposit an AlTiN layer. The second half's deposition time was 10minutes.

For sample 9, under the conditions for deposition as indicated in Table3 at the “conditions for depositing the AlTiN layer” column, the firstgas having the composition specified in table 4 by identification numberg, the second gas having the composition specified in Table 5, and thethird gas having the composition specified in Table 6 were jetted inthis order repeatedly onto a surface of the underlying layer to depositan Al₂O₃ layer. The deposition was done for 600 minutes.

For sample 10, under the conditions for deposition as indicated in Table3 at the “conditions for depositing the AlTiN layer” column, the firstgas having the composition specified in table 4 by an identificationnumber f, the second gas having the composition specified in Table 5,and the third gas having the composition specified in Table 6 werejetted in this order repeatedly onto a surface of the underlying layerto deposit an Al₂O₃ layer. The deposition was done for 10 minutes.

(Depositing the Surface Layer)

Under conditions indicated in Table 7 for deposition, a reactant gashaving a composition indicated in Table 7 was jetted onto a surface ofthe AlTiN layer to deposit a surface layer of TiN.

TABLE 7 conditions for depositing surface layer composition of reactantgas TiCl₄ = 0.5 vol %, N₂ = 41.2 vol %, H₂ = balance temperature 780° C.pressure 79.8 kPa gas flow rate 45.9 L/min

<Blasting>

The coating deposited on the substrate was blasted under the followingconditions (a third step):

(Blasting Conditions)

Medium: 500 g of zirconia particles

Projection angle: 90°

Projection distance: 50 mm

Projection time: 3 seconds

Through the above process, cutting tools were produced for samples 1 to10 indicated in table 8.

TABLE 8 coating's composition & conditions for each layer's thicknessdepositing AlTiN layer underlying surface 1st half 2nd half layer AlTiNlayer layer deposition deposition composition atomic composition totalsample 1st gas time 1st gas time (thickness: ratio x (thickness: coatingnos. (table 4) (min.) (table 4) (min.) μm) of Al (μm) μm) (μm) 1 g 590 a10 TiCN(4.8) 0.82 5.0 TiN(0.2) 10.0 2 g 587 b 13 TiCN(4.8) 0.82 5.0TiN(0 2) 10.0 3 g 583 c 17 TiCN(4.8) 0.82 5.0 TiN(0.2) 10.0 4 g 552 d 48TiCN(4.8) 0.81 5.0 TiN(0.2) 10.0 5 g 583 b 17 TiCN(4.8) 0.82 5.0TiN(0.2) 10.0 6 g 587 c 13 TiCN(4.8) 0.82 5.0 TiN(0.2) 10.0 7 g 548 d 52TiCN(4.8) 0.81 5.0 TiN(0 2) 10.0 8 g 552 e 48 TiCN(4.8) 0.81 5.0TiN(0.2) 10.0 9 g 600 — — TiCN(4.8) 0.82 5.0 TiN(0.2) 10.0 10 (f)  (10)— — TiCN(4.8) no AlTiN layer TiN(0.2) 10.0 (Al₂O₃ layer (5.0)) AlTiNlayer's oxygen content ratio 1st region 2nd region 3rd region distancedistance distance from 1st from 1st from 1st major major major cuttingtest sample surface max. value surface max. value surface max. valuedistance nos. (nm) (atom %) (nm) (atom %) (nm) (atom %) (km) damagedstate 1 16 40 36 24 104 4 6.0 normally worn 2 28 35 32 28 104 3 5.6normally worn 3 28 33 32 28 104 2 5.2 normally worn 4 28 31 96 7 104 14.8 normally worn 5 22 36 36 32 104 4 2.0 worn & broken 6 28 28 56 18104 4 1.8 welded & broken 7 28 32 90 20 104 7 2 0 worn & broken 8 20 2096 4 104 2 1.8 welded & broken 9 — 0 — 0 — 0 2.0 welded & broken 10 noAlTiN layer 2.2 flank significantly worn

<<Evaluating Characteristics of Cutting Tools>>

The cutting tools of samples 1 to 10 each underwent measurement of thethickness of each layer of the coating, the composition of the AlTiNlayer, and the oxygen content ratio of the AlTiN layer.

<Thickness of Each Layer of Coating>

The underlying layer, the AlTiN layer, the surface layer, and the entirecoating were measured in thickness with a scanning transmission electronmicroscope (STEM) (trade name: JEM-2100F, manufactured by JEOL Ltd.).How this measurement was specifically done will not be described as ithas been described in the first embodiment. A result is shown in table8, the “coating's composition and each layer's thickness” column, the“underlying layer,” “AlTiN layer.” “surface layer,” and “total coating”subcolumns.

For example, Sample 1 had an underlying layer which was a 4.8 μm-thickTiCN layer, an AlTiN layer which was a 5.0 μm-thick layer, a surfacelayer which was a 0.2 μm-thick TiN layer, and a coating having a totalthickness of 10.0 μm.

<Composition of AlTiN Layer>

The AlTiN layer was subjected to measurement of an atomic ratio x of Alin Al_(x)Ti_(1-x)N with an energy-dispersive-X-ray-analysis (EDX) device(SU9000® produced by Hitachi High-Tech Corporation) accompanying ascanning electron microscope (SEM). How this measurement wasspecifically done will not be described as it has been described in thefirst embodiment. A result is shown in table 8, the “coating'scomposition and each layer's thickness” column, the “atomic ratio x ofAl” subcolumn.

<Oxygen Content Ratio of AlTiN Layer>

The AlTiN layer's oxygen content ratio was measured with an Augerelectron spectrometer (device: PHI 650® produced by Perkin-Elmer). Howthis measurement was specifically done will not be described as it hasbeen described in the first embodiment. The measurement was conducted ina region having a distance of 0-200 nm in a depthwise direction from thefirst major surface of the AlTiN layer. A maximum oxygen content ratioin each of the first, second and third regions of the AlTiN layer andwhere it is measured (or a distance from a major surface) are indicatedin Table 8 at the “AlTiN layer's oxygen content ratio” column.

For example, sample l's AlTiN layer was measured, as follows: the firstregion had a maximum oxygen content ratio of 40 atomic % at a pointhaving a distance of 16 nm from a major surface, the second region had amaximum oxygen content ratio of 24 atomic % at a point having a distanceof 36 nm from the major surface, and the third region had a maximumoxygen content ratio of 4 atomic % at a point having a distance of 104nm from the major surface.

<<Cutting Test>>

(Cutting Evaluation: Continuous Processing Test)

The cutting tools of samples 1 to 10 were used to perform end-faceinching turning of chromium molybdenum steel under the following cuttingconditions. A cutting distance (in meters) reached when the flank wasworn by an amount of 0.25 mm or the cutting edge portion was broken wasmeasured. Moreover, how the cutting tools were damaged after cutting(i.e., a final damaged state) was observed. A result thereof is shown intable 8. A longer cutting distance indicates a longer tool life.

<Cutting Conditions>

Workpiece: SCM415 round bar with a work diameter of φ180

Rotational speed: 500 rpm, 5 s processing+0.5 s zero cutting

Feed rate: 0.2 mm/t

Cutting amount: 1.5 mm

Cutting oil: Dry type

<Discussions>

The cutting tools of samples 1 to 4 correspond to examples. The cuttingtools of samples 5 to 10 correspond to comparative examples. It has beenconfirmed that the cutting tools of samples 1 to 4 (examples) had longertool life than those of samples 5 to 10 (comparative examples).

It is believed that Samples 1 to 4 provided increased tool life as theAlTiN layer had the first region with a maximum oxygen content ratio of30 atomic % or more and hence excellent welding resistance, the secondregion with a maximum oxygen content ratio of 5 atomic % or more andless than 30 atomic %, and the third region with a maximum oxygencontent ratio of less than 5 atomic %, and accordingly, the AlTiN hadhigh hardness as a whole and excellent wear resistance.

Sample 5 was worn and broken. It is believed that this is because insample 5 the AlTiN layer had the second region with a maximum oxygencontent ratio of 32 atomic % and thus had a large amount of oxygen in adeep portion thereof, resulting in a reduced film hardness.

Sample 6 was welded and broken. It is believed that this is because insample 6 the AlTiN layer had the first region with a maximum oxygencontent of 28 atomic % and hence reduced welding resistance.

Sample 7 was worn and broken. It is believed that this is because insample 7 the AlTiN layer had the third region with a maximum oxygencontent ratio of 7 atomic % and thus had a large amount of oxygen in adeep portion thereof, resulting in a reduced film hardness.

Sample 8 was welded and broken. It is believed that this is because insample 8 the AlTiN layer had the first region with a maximum oxygencontent of 20 atomic % and hence reduced welding resistance and thesecond region with a maximum oxygen content of 4 atomic % and henceinsufficient heat resistance.

Sample 9 was welded and broken. It is believed that this is because insample 9 the AlTiN layer had the first region with a maximum oxygencontent of 0 atomic % and hence reduced welding resistance, and thesecond region with a maximum oxygen content of 0 atomic % and henceinsufficient heat resistance.

Sample 10 had a flank significantly worn and thus had a short tool life.It is believed that this is because in sample 10 no AlTiN layer existsand an Al₂O₃ layer having low hardness exists.

While embodiments and examples of the present disclosure have beendescribed as above, it is also planned from the beginning that theconfigurations of the above-described embodiments and examples areappropriately combined and variously modified.

The embodiments and examples disclosed herein are illustrative in anyrespects and should not be construed as being restrictive. The scope ofthe present invention is defined by the terms of the claims, rather thanthe above-described embodiments and examples, and is intended to includeany modifications within the scope and meaning equivalent to the claims.

REFERENCE SIGNS LIST

1, 21, 31 cutting tool, 10 substrate, 11 AlTiN layer, 11 a first majorsurface, 11 b second major surface, 11A first region, 11B second region,11C third region, 12 underlying layer, 13 surface layer, 14, 24, 34coating, 50 CVD apparatus, 52 substrate setting jig, 53 reactionchamber, 54 temperature controller, 55 first gas introduction pipe, 56second gas introduction pipe, 57 third gas introduction pipe, 58 gasintroduction pipe, 59 gas exhaust pipe, 60 gas exhaust port

The invention claimed is:
 1. A cutting tool comprising a substrate andan AlTiN layer disposed on the substrate, the AlTiN layer includingcubic Al_(x)Ti_((1-x))N crystal grains, an atomic ratio x of Al in theAl_(x)Ti_((1-x))N being 0.7 or more and 0.95 or less, the AlTiN layerincluding a first major surface on a side of a surface of the cuttingtool and a second major surface on a side of the substrate, the AlTiNlayer including a first region having a distance of 0 nm or more and 30nm or less from the first major surface, a second region having adistance of more than 30 nm and 100 nm or less from the first majorsurface, and a third region having a distance exceeding 100 nm from thefirst major surface, the first region having a maximum oxygen contentratio of 30 atomic % or more, the second region having a maximum oxygencontent ratio of 5 atomic % or more and less than 30 atomic %, the thirdregion having a maximum oxygen content ratio of less than 5 atomic %. 2.The cutting tool according to claim 1, wherein the first region has amaximum oxygen content ratio of 30 atomic % or more and 50 atomic % orless.
 3. The cutting tool according to claim 1, wherein the AlTiN layerhas a thickness of 0.1 μm or more and 20 μm or less.
 4. The cutting toolaccording to claim 1, further comprising an underlying layer disposedbetween the substrate and the AlTiN layer, wherein the underlying layeris composed of a first compound consisting of: at least one elementselected from the group consisting of a group 4 element, a group 5element and a group 6 element of the periodic table and Al; and at leastone element selected from the group consisting of carbon, nitrogen,oxygen and boron.
 5. The cutting tool according to claim 1, furthercomprising a surface layer disposed on the AlTiN layer, wherein thesurface layer is composed of a second compound consisting of: at leastone element selected from the group consisting of a group 4 element, agroup 5 element and a group 6 element of the periodic table and Al; andat least one element selected from the group consisting of carbon,nitrogen, oxygen and boron.